In the operation of conveyor systems, and especially trolley wheel and support assemblies in overhead systems, including power and free systems, or trolley assemblies including wheeled carrier supports in floor conveyor systems, significant problems result from the rotation of the various parts in such assemblies during operation. Conventionally known bolts and/or rivets, which are typically used to secure trolley brackets to trolley wheel assemblies which ride on overhead conveyor tracks, have been relied on for a dual function of both retaining the various parts together and also keeping sufficient force, i.e., compression, on such parts to prevent their rotation during use. However, loosening of the various assembly parts around such bolts or rivets in operation causes rotation and allows the parts to move axially apart from one another in the assembly, resulting in several problems. Such problems include the loss of full support for the ball or rolling elements in full ball complement trolley wheels, the premature wear and failure of the wheel support areas of trolley brackets, the premature wear and failure of the supporting shaft such as the rivet or bolt, and the inability to properly drain or remove contaminants from the wheel bearing assembly. In addition, prior known assemblies provided less than optimum load bearing capabilities and weight distribution within such assemblies.
A concurrent problem with prior known trolley assemblies was the lack of ability to easily assemble and disassemble the trolley wheel assembly from the support or trolley bracket in the overhead conveyor system. In many cases, it is desired to disassemble and replace a trolley wheel in an overhead system without removing the trolley brackets from the overhead conveyor chain and without disassembling the conveyor chain which is a laborious task. The problem is especially acute in fully closed or sealed wheel assemblies having lubrication seals or closure members completely enclosing the rolling element receiving area between the inner and outer races of such assemblies. Such assemblies may be either permanently lubricated or include relubrication features. In such situations, access to the supporting shaft, bolt or rivet is impossible because of the enclosed nature of the wheel assembly. Accordingly, there is no easy way to hold the bolt and remove the nut from the bolt to enable removal of the wheel assembly from the trolley bracket. In such cases, it was often necessary to remove the entire trolley bracket from the chain and remove one or more of the shields or closure members from the wheel in order to remove the wheel assembly from the trolley or support bracket.
An attempt at solving the above problems in a trolley bracket and wheel assembly is shown in U.S. Pat. No. 3,553,765. This assembly requires a special trolley bracket having a machined projection including flat surfaces which engage corresponding flat surfaces on a specially formed, lateral extension of a one-piece inner race of a wheel assembly, as well as a shield member on one side of the wheel. A circular bolt extends through all of the parts and engages threads on the inner race to hold the parts together. This structure, however, cannot be used with stamped, sheet metal or conventional forged trolley brackets because of the required, specially formed bracket extension. Further, the use of multi-part inner races and full ball complement wheels is difficult with such structure because of the required, one-piece inner race and lateral extension to prevent rotation. Also, a special locking washer engaging the bolt and bracket must be used to prevent bolt rotation. Load distribution is also less than optimum because the circular bolt cannot distribute loads over a wide base area. The provision of specially machined parts is also very expensive and detracts from the acceptance of the assembly.
Another trolley bracket and wheel assembly in which a portion of the various inner race and bracket parts are nonrotational is shown in U.S. Pat. No. 3,971,601. This structure does not include any shield or seal structure at all, let alone a shield structure which prevents rotation. Also, all parts of the inner race assembly are not positively prevented from rotating, especially if loosening of the assembly occurs. Further, load distribution is again less than optimum.
In one such system, a small, separate key is fitted between a milled slot or keyway in a supporting shaft for a wheel on a four wheel carrier assembly and the inner race of a wheel, a shield member and a central support member or casting in such an assembly. The small key is very difficult to assemble and maintain, in addition to requiring a much greater expense for machining various keyways and corresponding shapes in the mating parts. Moreover, such wheel assemblies require removal of closure/shield members before the assembly can be removed or disassembled, do not provide advantageous weight or load distribution, and rely greatly on the relatively small key which, if broken or distorted, cannot prevent the rotation and consequent loosening of the assembly discussed above. In actual practice, such keys and keyways have been found to have an unacceptable failure rate.
The present invention provides a solution to the above-noted problems in the support and use of trolley assemblies in various conveyor systems.